CAJ | 학술논문

报道了大别山北部三个榴辉岩样品的矿物Sm-Nd等时线年龄，它们分别为(210±6)Ma或(214±6)Ma、(208±38)Ma和(208±4)Ma。氧同位素研究表明，这些样品中的石榴子石与绿辉石之间处于氧同位素平衡状态，因此，该Sm-Nd等时线定年结果可靠。本区榴辉岩的高压麻粒岩相退变质阶段的冷却年龄为210Ma左右；榴辉岩的钕同位素初始比εNd(t)(两个样品一个为-10左右，另一个为-2)基本上表现为陆壳岩石特征，可能类似于南部超高压带中的榴辉岩，为印支期扬子陆壳俯冲变质成因。它们的全岩δ18O值较低，为+2.4‰～+3.6‰，可能指示其原岩同大别山南部超高压带中榴辉岩一样，在板块俯冲之前，经受过高温地表水热液蚀变。年代学结果表明，大别山北部榴辉岩在230～210Ma期间经历的是一等温或升温过程，这与大别山南部含柯石英榴辉岩在这一时期的快速冷却过程形成强烈对比，这对理解俯冲陆壳中不同构造岩片折返过程的差异有重要意义。
보도료대별산북부삼개류휘암양품적광물Sm-Nd등시선년령，타문분별위(210±6)Ma혹(214±6)Ma、(208±38)Ma화(208±4)Ma。양동위소연구표명，저사양품중적석류자석여록휘석지간처우양동위소평형상태，인차，해Sm-Nd등시선정년결과가고。본구류휘암적고압마립암상퇴변질계단적냉각년령위210Ma좌우；류휘암적녀동위소초시비εNd(t)(량개양품일개위-10좌우，령일개위-2)기본상표현위륙각암석특정，가능유사우남부초고압대중적류휘암，위인지기양자륙각부충변질성인。타문적전암δ18O치교저，위+2.4‰～+3.6‰，가능지시기원암동대별산남부초고압대중류휘암일양，재판괴부충지전，경수과고온지표수열액식변。년대학결과표명，대별산북부류휘암재230～210Ma기간경력적시일등온혹승온과정，저여대별산남부함가석영류휘암재저일시기적쾌속냉각과정형성강렬대비，저대리해부충륙각중불동구조암편절반과정적차이유중요의의。
Sm-Nd and oxygen isotope ratios of garnet and omphacite fromeclogites in North Dabie Mountains were measured along with their petrological features. Unlike coesite-bearing eclogites in South Dabie Mountains which underwent amphibolite-facies retrogression, the eclogites in North Dabie Mountains suffered granulite-facies overprinting. Relationship between the δ18O values of the eclogite minerals suggests oxygen isotope equilibrium fractionation, corresponding to the Sm-Nd isotope equilibrium between the minerals according to comparability between O and Sm-Nd diffusivities. The δ18O values of whole-rocks for the eclogites are + 2. 4‰ to + 3.6‰, indicating that the eclogites underwent the hydrothermal alteration of high-temperature surface water prior to the subduction of the Yangtze continental plate. The Sm-Nd isotope ages for the three samples of eclogites are identical with 210 Ma and they are interpreted to represent the cooling ages in the retrogressive stage of granulite-facies metamorphism. The initial ratios of Nd isotope for the eclogites are negative with εNd(t) = - 10 (two samples) and-2 (one sample), implying that they were derived from the subducted Yangtze continental crust like the eclogites in South Dabie. There is the isothermal or temperature rise history from 230 to 210 Ma for the eclogites in North Dabie, which is in contrast to that of the eclogites in South Dabie. This places important constraint on exhumation processes of the eclogites in northern and southern Dabie blocks.